During this part of the life cycle assessment, the results of the inventory analysis and impact assessment are evaluated for the products, processes, or services under study. This phase should include a clear understanding of any uncertainty in the data and the assumptions used to generate the results. In principle, this may sound simple, and in theory we would have a system such as the one described in Example 16.3, where it was clear from both the inventory and the impact assessment which route has the lowest impacts. But what happens when that is not the case? It is relatively common that with a long list of impacts to evaluate, one can find that process A might have a better profile than process B in some impacts, but worse in the remaining impacts. One must therefore come to terms with these trade-offs between environmental impacts during the decision-making process. Whether the trade-offs are important or not generally depends on the specific priorities of the decision makers, how large a difference there is among the trade-offs, and how much uncertainty there is in the data quality or overall assessment.
Example 16.4 Which is better: reformulated gasoline containing ethanol or conventional gasoline?
FIGURE 16.10 Results of the life cycle impact assessment for Example 16.3 using the CML method for global warming potential (a), eutrophication potential (b), acidification potential (c), and ozone depletion potential (d). (From ref 32.)
Solution It depends on those impacts with which you are most concerned. Different assessments to date have found that reformulated gas with ethanol is consistently better in terms of some impacts (e.g., global warming potential, fossil fuel use, ozone depletion potential), but it is consistently worse in terms of others (e.g., eutrophication potential, acidification potential, photochemical ozone creation potential). For example, Table 16.6 shows a qualitative comparison between reformulated gas with ethanol and conventional gasoline using a 5% cutoff rule and TRACI to estimate the impact assessment.36 Additional Points to Ponder What would be the effect of a change in land use to grow biofuel and biofeedstock materials? What happens when people report only one impact?
As can be seen from the biofuel example above, transparency once again plays an important role in the decision-making process. Some people tend to report only one or two impact categories, either because they desire to simplify the results of the life cycle assessment, lack experience in LCI/A, or lack a sufficient understanding of the life cycle and its nuances. This can be extremely misleading if there are some environmental impact trade-offs that are not being identified or considered, or if the environmental impact categories do not render the same results using different assessment methods.
Here are some important considerations to keep in mind when making decisions based on life cycle impact assessments or life cycle inventory assessments:
. The goal and scope of the LCA. One cannot easily extrapolate from one system to another unless the data and science support it.
. Boundaries and boundary conditions are extremely important. In comparative LCI/As these are fundamental, but it is even more important when talking about stand-alone LCAs, as the differences in boundaries can mean different outcomes.
. The degree of uncertainty in the data and the associated results. This is especially important when comparing outputs. How significant are the differences?
. Sensitivity of the results to variations in specific parameters. If other databases or assessment methods were used, would the results remain valid?
. Trade-offs. Are all the important impacts considered, or are there hidden trade-offs in the assessment results?
TABLE 16.6 Qualitative Comparison of Life Cycle Impact Assessment Results Between Reformulated Gasoline with Ethanol vs. Conventional Gasoline
Impact Category
Ranking of Reformulated Gasoline with Ethanol Compared with Conventional Gasoline
Ecotoxicity Worse
Eutrophication Worse
Acidification Worse
Photochemical smog Worse
Human health criteria Worse
Global warming Better
Human health noncancer Better
Ozone depletion Better
Fossil fuel use Better
Source:ref. 36.
data might cause important differences.
. Organizational values. Which impacts are valued above others, and do these align with the inherent priorities of the impact assessment methods employed?
. Micro- and macroeconomic factors. From a holistic viewpoint, would the total cost of the activity change the results? Are market forces affecting the assessment in some way?
. Societal values. Are there cultural impacts that might not be immediately apparent in the metrics used for the assessment?
Another example of life cycle concepts being used in industry is found in the ecoeffi- ciency and SEEBalance assessments developed by BASF.37In the BASF methodology, the ecoefficiency assessment attempts to measure both environmental and economic factors within a life cycle assessment framework. BASF has been using these assessments since 1996 on numerous products and processes as a means to achieve constant improvement in environmental and economic performance.
Some examples where the tool has been applied include the selection of the best synthetic route to indigo based on an assessment of four different technologies for indigo production; the assessment of two methods for cereal crop preservation to serve as a basis for discussing chemical additives in animal feeds, the analysis of two furniture board processes, which aided in making technology investment decisions; and others.38 According to the BASF Web site, results of the ecoefficiency analysis are intended to inform business decisions about:
. Whether or not further improvements are possible or if the assessment can be used as a selling point when the analysis confirms a high degree of ecoefficiency.
. Whether and to what extent the economic or ecological footprint can be improved when the analysis shows that a product or process has inadequate ecoefficiency but it is possible to improve it.
. Whether to abandon or substitute a product or process when the analysis shows that it has poor ecoefficiency and cannot be improved with a reasonable investment.
. Whether to direct further research and development to the most ecoefficient alternative when a product or process is in the early stages of research and there are several credible paths for further development to follow.
16.3.1 Presenting LCI/A Results
There are certainly many different ways to present the results of an LCI/A, depending on the type of information to be presented, the goal of the LCI/A study, and the stakeholders for the assessment. In a few words, the results and the corresponding information should strive to answer the question posed in the goal and scope definition and be easy to understand by the intended audience. In many situations, the same results need to be presented in several different ways to convey the appropriate and desired message. This can be done:
. Quantitatively. The results may be presented in terms of the LCI (Figure 16.9) or LCI/A results (Figure 16.10). Depending on what question is being answered,
the information may be presented in such a way that additional information is easy to obtain. For example, one might choose to show the results in terms of a:
Dominance analysis. This can be used to ascertain which of the life cycle phases or activities contribute most to the environmental footprint (Figures 16.11 and 16.12).39
Contribution analysis. Similar to the dominance analysis, but instead of deter- mining those activities with the largest contributions, it focuses on environ- mental loads or emissions (Figure 16.13).40
Break-even analysis. This serves to determine environmental impact trade-offs or to set goals for product development41(Figure 16.14).
Data quality analysis. This can be expressed in terms of sensitivity or uncertainty analysis (Figure 16.7). Data quality indicators can also be used as a semi- quantitative assessment uncertainty of the LCI/A.42
. Qualitatively. Some times it is desired to maintain a very high level of detail as a means of showing contrast or identifying hot buttons on an LCA (Table 16.6).
Example 16.5 An ecoefficiency analysis was performed to compare the life cycle environmental impacts and costs for BASF and several competitors to produce ibuprofen.
The basis for the assessment was the production of 1 kg of ibuprofen for use in over-the- counter pain relief medication sold in North America. The processes being compared were:
. Ibuprofen produced by BASF in the United States
. Acetylchloride and cyanohydrin chemistry in the United States
. Acetylchloride, glycidester, and Cr(VI)-oxidation chemistry in India
. Chlorpropionylchloride and rearrangement chemistry in China
100%
80%
60%
40%
20%
0%
Total cradle materials (kg) Energy (MJ)
TOC (kg) POCP (kg.et) GHG (CO2-eq) Acidification (SO2-eq) Eutrophication (PO43–-eq.)
Chemicals Solvents Internal
FIGURE 16.11 Cradle-to-gate LCA pretreatment contributions of solvent manufacturing, pro- duction of nonsolvent chemicals, and internal active pharmaceutical ingredient manufacturing.
(From Jime´nez-Gonza´lez et. al, ref 39. Reproduced with kind permission from Springer Science and Business Media. CopyrightÓ2004, Springer Science and Business Media.)
The results of the assessment are presented in Figures 16.15 and 16.16. What conclusions can be drawn from the assessment?
Solution In general, the ibuprofen produced by BASF is more ecoefficient, followed closely by the U.S. competitor. The ibuprofen produced in the United States costs more
100 90 80 70 60 50 40 30 20 10 0
Emission air
Impact [%]
Emission surface
water
Emission ground
water
Emission top soil
Energy resources
Natural resources
Deposited waste Y
X
FIGURE 16.13 Impact of X compared to Y. The hatched portion of the emission air segment represents the combustion gases (CO2, NOx, SO2) from energy production. (Source: ref 40, Reproduced with permission.)
180%
160%
140%
120%
100%
80%
60%
40%
20%
0%
Total cradle materials (kg) Energy (MJ) TOC (kg, 86% reduction) POCP (kg.et, 45% reduction) GHG (CO2-eq) Acidification (SO2-eq) Eutrophication (PO43–-eq. 52% reduction)
Percentage relative to pretreatment value
Process Energy Transport Treatment
FIGURE 16.12 Cradle-to-gate LCA posttreatment contributions of energy, production processes, transportation, and treatment systems for pharmaceutical active ingredient manufacturing. (From Jime´nez-Gonza´lez et. al, ref 39. Reproduced with kind permission from Springer Science and Business Media. CopyrightÓ2004, Springer Science and Business Media.)
FIGURE 16.15 Ecoefficiency and footprint comparisons for the BASF example. (Source: ref 38, Reproduced with permission from BASF.)
4.0
LCA score
3.5 3.0 2.5 2.0 1.5 1.0
0 10 20 30
Solvent Recovery (wt%)
40 50 60 70 80 90 100
Bio Chem
FIGURE 16.14 Break-even analysis of an LCA score that shows the environmental profile of a chemical process (Chem) and a biocatalytic process (Bio) at different theoretical scenarios for solvent recovery. (Source: ref 41.)
479
than ibuprofen produced in India or China at the time of the assessment. These costs are somehow a result of the resources used to optimize their processes, maintain and operate their equipment to prevent contamination, and ensure that the environment and the workers are protected. However, from an environmental perspective, U.S. produced ibuprofen has significantly lower impacts than those of the ibuprofen produced in other countries. Some examples of background calculations used in the life cycle assessment (Figure 16.5) show the toxicity potential of the materials used during production, the disposal impacts due to accidents and waste, and the use impacts. The toxicity potential of the U.S.-based production is much less because closed-loop manufacturing systems are used, which protect workers from exposure to the materials being handled. The impacts for disposal reflect the quantities of hazardous materials and the safety and environmental controls that are present. During the use phase, the most significant differentiating factors are the transportation distances and the safety and environmental practices that are in place at the various manufacturers.
Additional Points to Ponder What is the relevance of the different processes used?
How would you interpret the trade-offs between health and emissions in the ecological footprint?
16.3.2 Limitations of LCI/A
Although life cycle inventory and assessment is a very powerful tool, as is the case with any methodology, there are limitations in its application. First, performing a full LCI/A can be resource and time intensive, especially if not enough data are readily available, or if one’s knowledge of the system under study is limited. In many instances, available data are limited, and for those data that are readily at hand, there is likely to be greater uncertainty associated with these data than what one might be willing to accept. One may therefore wish to weigh the ability to obtain a sufficiently complete data set against the desired degree of accuracy that one believes is necessary for the study to be credible. In almost all LCI/A studies one will inevitably be faced with having to make some assumptions about the source data or will be forced to utilize averaged data from multiple sources (i.e., background data).
As has been stated repeatedly above, these inherent limitations in LCI/A studies necessitate that one maintains transparency about the assumptions and the data quality for any data used in the study. Transparency ensures that there is an explicit demarcation of the sources, assumptions, information utilized, and data gaps within a life cycle inventory or assessment. LCI/A is an iterative methodology, and very seldom is it the case that an LCI/A result is fixed; thus, data transparency will help greatly to bolster the credibility and acceptance of the study while making it easier to integrate more accurate information as new data become available.
In addition to problems or issues with data limitations, when seen within the broader sustainability context, LCI/A is a methodology that needs to continue to evolve with the state of the art and science. Although LCI/A is arguably the most holistic sustainability methodology at the moment, social or economic aspects have historically been out of the scope of traditional LCI/As. However, it should be noted that other tools, such as social LCA and total cost accounting (life cycle costing), tend to cover these aspects (see Chapter 20).
As we saw in Section 16.3.2, LCI/A methodology has several limitations, many of them linked to the transparency of the underlying data, the assumptions, and the methodology used to undertake the assessment. In some LCAs, particularly those used to assess high-profile commercial, societal, or policy questions, there have been concerns that the practitioners might be trying to demonstrate a specific point of view instead of looking for a scientifically defensible explanation. In an attempt to ensure the credibility of LCI/A methodology and to answer concerns about objectivity, there has been a movement toward increased standardi- zation of LCI/A methodologies and critical peer reviews.
Besides enhancing credibility, critical peer review helps to maintain data confidentiality and integrity by allowing a reviewer to validate the study as they review the entire assessment. This allows the final results to be communicated with confidence without having to show the confidential information. In addition, as one delves more deeply into LCI/A and develops greater experience with it, it becomes clear that performing a high- quality assessment is more complex than one might at first think upon learning the conceptual idea of the cradle-to-grave assessment. A critical reviewer can therefore help the practitioner to choose the appropriate and relevant methodology to achieve the goal of the study or might help to ensure that the ISO standards are maintained. Finally, when the results of the LCA may possibly affect policy or market decisions, inviting interested parties and stakeholders as part of the critical review is an advisable option.
The ISO standard contemplates three types of reviews: review by internal experts, review by external experts, and review by interested parties. Reviews performed by interested parties are normally done as a panel of experts, whereas internal and external expert reviews tend to be done by a single reviewer. Not all LCAs are subject to critical review, but it is definitely advisable to consider it in the planning. In addition, not all critical reviews are the same. The ISO standards recognize two comprehensive and formal critical reviews:
. The ISO standard full review, which is mandatory in cases where comparative assess- ments are done for a public audience in mind. The primary focus of this review is on the methodology, its consistency with the ISO standard, and its scientific validity.
. The review of environmental product declarations, where the primary focus is on the underpinning data. In these cases, customers are expected to draw conclusions and comparisons based on potentially nontransparent (commercially sensitive or proprie- tary) aggregated data.
There are very specific guidelines for these two types of mandatory critical reviews. In contrast to these reviews, the focus of the internal expert or external expert reviews will need to be decided as part of the goal and scope of the LCA in question.